Mouldings based on fibrous webs are widely used in industry. These comprise felts made of fibres of various types which may be mixed with binders. Preliminary products, which are termed prepregs (chemically bonded fibrous webs) can be produced from these fibrous webs, and are then moulded, cured and optionally cut to size using corresponding processing tools. It is also possible to produce corresponding continuous products made of fibrous web directly from the fibres and binder powders. These mouldings or flat goods have a wide range of uses. In the automobile industry, for example, these products are used as mouldings, e.g. as an insulating material for engine compartments or wheel guards, or as boot compartment insulation. Another area of use is their use as flat goods, e.g. as an insulating material in washing machines, linen dryers or loudspeakers, in sound-absorbing walls. They can be provided with additional coatings, e.g. by flock coating, covering or laminating. These mouldings or flat parts which are thus provided with a visually stable and decorative surface coating can then be used, for example, as door trims, hat racks or roof linings in the automobile industry.
A fibrous web material is understood to be a bonded textile material which is produced by the consolidation of fibrous web, particularly spun-bonded web (e.g. parallel, crossed or matted fibrous web), by a wet or dry route. In the course of this procedure, consolidation is effected mechanically (e.g. needled felt) or in the manner of paper manufacture with the aid of cellulose fibres, or chemically by adhesive bonding, bonding or dissolution. The present invention relates to the last-mentioned case, in which a binder is added for the chemical consolidation of the fibrous web.
Methods of producing fibrous webs and mixing these webs with binder powders are known. In the course of these methods, the fibrous material is homogenised, e.g. in a fibre mixing chamber, and is deposited on a conveyor belt as a loose fibrous layer.
The binder mixture is then applied to the fibrous material, e.g. by metering rolls or vibrating troughs, and is homogeneously mixed. The homogeneous mixture of fibres and binder powder is deposited to form a continuous fibrous web. The components of this mixture may either be adhesively bonded to each other by slight heating and subsequent cooling, whereupon prepregs are formed, or flat or rolled goods may be produced which are already fully cured. The prepregs are not yet finally cured, but are stable on storage. After processing into their final form, these prepregs are thermally crosslinked under the action of heat at temperatures up to 210.degree. C., whereupon three-dimensional thermosetting plastics mouldings are obtained.
Thermosetting plastics, and particularly phenolic resins here, are nowadays used as binders in many cases. Fibrous webs and fibrous web mouldings are used in many areas of daily life, and are also used in the automobile industry in particular. Difficulties can arise in use, since phenolic resins contain the chemical compound hexamethylene tetramine, abbreviated to hexa, as a curing component, which can result in an odour nuisance if insufficient reaction takes place.